Hi! I would like to contribute with this plugin, with some custom validation methods for spanish documents.

NIF It is like US Social Security Number, or the UK National Insurance Number for an individual. CIF it's the same but for companies.

The NIE (Número de Identificación de Extranjero) is the counterpart to a NIF for Spanish citizens. The NIE is the identification number in Spain for everyone who is not a Spanish citizen.

http://moreovercoder.blogspot.com.es/2013/07/validacion-de-nie-nif-y-cif-con-jquery.html

Hope this helps!